Field of the Invention
The present invention relates to a reference voltage generation circuit, and in particular, is useful when applied to a voltage source driving a semiconductor product being used in a wide temperature range.
Background Art
In recent years, an operating temperature range (for example, −50° C. to 150° C.) required for a semiconductor product tends to expand, and in a reference voltage generation circuit of the related art which regulates a reference output voltage with a normal temperature as 25° C., there is a problem in that a predetermined reference output voltage cannot be obtained with high precision and stably in a wide temperature range. In particular, whereas a reference output voltage of a semiconductor product for a power supply requires flat temperature characteristics in a wide temperature range, in a regulator, a switching power supply, or the like, a temperature inside an IC becomes a high temperature due to heat generation or the like. As a result, in the reference voltage generation circuit of the related art, there is a problem in that load stability is deteriorated.
JP-A-2013-161258, JP-A-2014-186714, JP-A-2008-293409 suggest a reference voltage generation circuit which is contrived such that flat temperature characteristics are obtained.
While the technique described in JP-A-2013-161258 is intended to output low power with a small minimum operation voltage and to obtain flat temperature characteristics arbitrarily, basically, since flat temperature characteristics in a predetermined range are obtained by one reference voltage source, it is not sufficient for making temperature characteristics flat in a wide temperature range of, for example, −50° C. to 100° C.
JP-A-2014-186714 relates to a technique contrived such that, even if variation exists in a manufacturing process, flat temperature characteristics can be obtained. However, since a reference voltage generation circuit disclosed in JP-A-2014-186714 forms a plurality of unit reference voltage generation circuits in parallel, and then, selects a unit reference voltage generation circuit having the flattest temperature characteristics among a plurality of unit reference voltage generation circuits, the remaining unit reference voltage generation circuits have to be discarded, causing deterioration of yield. Also, the temperature characteristics are not essentially different from those in a case where the reference voltage generation circuit is formed of one reference voltage source, and sufficient flattening of the temperature characteristics in a wide range cannot be implemented.
JP-A-2008-293409 relates to a technique contrived so as to reduce variation in reference voltage due to process fluctuation, temperature fluctuation, and power supply voltage fluctuation. However, like JP-A-2013-161258, since JP-A-2008-293409 relates to a technique contrived such that flat temperature characteristics in a predetermined range are obtained by one reference voltage source, it is not sufficient for making the temperature characteristics flat in a wide temperature range.